Lava damage's type

I think it's actually counted as debuff sort of like poison/dischord and it can't be reduced.

That wouldn't be plausible if you're able to run out of the lava to avoid damage, as stated in the details.

I know it's unlikely, but it could be a debuff that depends more on location than time, or a debuff that only deals damage once but keeps reactivating if you stay in the area, like a shorter version of sulfur poisoning. That's why I'm asking, I'm only like 80% sure that DevCat would make this Magic.

If I'm not mistaken, Dischord can be reduced by Physical Defense/Protection. Wouldn't Meteor Strike be reduced by Magic Defense/Prot?

I think that technically, the debuff damage from dischord is only indirectly reduced because it's base is based on the player's dmg range against that target.